Needle stick injuries, e.g., among medical personnel such as health care workers, are of growing concern because of disease transmission, particularly the deadly virus known as HIV-1 (AIDS) and Hepatitis B. With presently used syringes having projecting needles, potentially dangerous needle stick injuries are commonplace and most often occur between the time medication is injected into the patient and the time of the disposal of the syringe. Most injuries occur while recapping the needle or when disposing it into a disposal, e.g., "sharps," container. Maintenance personnel who handle disposed materials are also subject to needle stick injuries.
These concerns have been previously addressed as described in our prior U.S. patents and patent application listed above. In these documents, there is disclosed a syringe comprised of a hollow, elongated barrel, an adapter secured to an end of the barrel and releasable therefrom by rotation of the adapter relative to the barrel for withdrawal into the barrel, a plunger movable axially within the hollow barrel, and cooperative engagement structures on the adapter and at the end of the plunger proximate the adapter for engaging and rotating the adapter relative to the barrel to enable the adapter and the needle carried thereby to be withdrawn into the interior of the barrel. Various apparatus are employed to seal the opposite ends of the barrel once the adapter and needle have been withdrawn into the barrel, thereby providing effective protection against potentially dangerous needle stick injuries and contamination by leakage of fluids from the syringe.
It will be appreciated from a review of our prior patents and pending application that the needle can be provided integrally with the adapter or may be provided separately of the syringe. For example, a needle assembly comprised of a needle hub, a needle secured to the hub and a needle guard encasing the needle and at least in part the hub may be provided for attachment by the user of the syringe to the barrel or the adapter. Typically, the needle assembly is secured to the syringe by either a Luer lock or a Luer fit. In both cases, the needle assembly normally includes a needle hub having radially outwardly projecting flanges. In a Luer lock, the needle is secured to the syringe by threading the flanges along a partially female threaded interior portion of the barrel. Alternatively, the needle hub may be frictionally engaged with a projecting tapered fitting on the barrel end. This is typically characterized as a Luer fit and does not have any positive locking action between the needle hub and the tapered projection on the barrel end, other than the frictional engagement. Thus, when a Luer lock is employed, the user of the syringe typically rotates the needle assembly, i.e., the needle guard, needle and needle hub, to positively engage the needle hub with the barrel end. When using a Luer fit, however, only an axial force on the needle assembly toward the syringe is necessary to frictionally engage the needle hub and the tapered projection on the barrel end. In typical syringes, the Luer fit comprises an integral part of the barrel or is at least non-rotationally secured to the barrel.
As a consequence, when attaching needle assemblies to a conventional syringe, frequent users of such syringes typically reflexively rotate the needle guard and needle hub, usually without regard to whether the securement is a Luer lock or a Luer fit (the latter, of course, does not require any rotation for securement of the hub to the barrel end as explained above). Also, when removing the needle assembly from the syringe, for example, when changing needles on the same syringe, the user will typically apply the needle guard and rotate the needle guard and hub relative to the tapered fitting on the barrel to essentially unscrew the hub from the barrel in the case of a Luer lock and to break the static friction between the hub and the fitting in the case of both the Luer lock and Luer fit. Consequently, a rotational force or torque is usually applied to the needle guard to remove a needle from a conventional syringe having a fixed or integral tapered fitting and without consequence to the syringe. However, with the advantageous arrangement of an adapter being removably mounted in the end of the syringe barrel in response to joint rotation of the plunger and adapter when the plunger engages the adapter (as set forth in the above-identified patents and patent application), there is a potential that this reflexive action of the user or any torque applied by the user, intended or otherwise, when applying the needle assembly to or removing it from the syringe could apply sufficient torque to the adapter to unseat the adapter from the syringe from its sealing engagement in the end of the barrel. This inadvertent unthreading or rotation of the adapter relative to the barrel end is highly undesirable, particularly from the standpoint of the close of the seal between the adapter and barrel end which, in turn, would result in fluid leakage. Contamination, in this type of syringe, may also be a problem should the seal be broken by this unthreading action.
According to the present invention, there is provided a needle guard and needle assembly for use with syringes of the type having an adapter removable from the syringe barrel end by rotation of the adapter relative to the barrel end, e.g., to withdraw the needle into the barrel, wherein inadvertent or intentional application of torque to the needle assembly when applying or removing it relative to the syringe will preclude application of torque to the adapter or torque of a magnitude sufficient to unseat the adapter relative to the barrel, and hence prevent the adapter from being unseated from the barrel when applying or removing the needle assembly. To accomplish this, the needle guard and needle hub have cooperable surfaces configured such that a torque applied to the needle guard in one direction is transmitted to the needle hub whereas a torque applied to the needle guard in the opposite direction enables relative rotation of the needle guard and the needle hub without transmission of substantial torque from the needle guard to the needle hub. Thus, if the adapter may be unthreaded from to the barrel end in response to a torque applied to the adapter in one rotational direction, the cooperable surfaces of the needle guard and needle hub are configured such that any torque transmitted from the needle guard to the needle hub in that one direction is insufficient to cause the adapter to unthread from the barrel end. That is, should a torque be applied to the needle guard in the unthreading direction of the adapter, the needle guard will generally freely rotate relative to the hub or will not transmit sufficient torque to the needle hub to cause separation of the adapter from the barrel end. Conversely, a torque applied to the needle guard in the opposite direction may be desirably selectively transmitted to the hub, for example, to break the static friction between the needle hub and the Luer fitting of the adapter so that the needle may be removed from the syringe when changing needles for use with the same syringe. Consequently, the cooperable surfaces of the needle guard and needle hub permit a positive torque to be intentionally applied to the needle hub from the needle guard to break that static friction, but only if the torque is applied in a direction opposite the unthreading direction of the adapter relative to the barrel.
In a preferred embodiment according to the present invention, there is provided apparatus for releasably securing a needle to an end portion of a syringe comprising a needle hub having a needle projecting from one end thereof and a passage through the needle for transmission of a fluid, the needle hub having a surface for engaging the end portion of the syringe and a needle guard including a sleeve closed at one end and open at its opposite end for receiving the needle and a portion of the needle hub within the sleeve, the needle guard and the needle hub having cooperable surfaces, respectively, configured to transmit a torque applied to the needle guard in a first direction to the needle hub and to enable relative rotation of the needle guard and the needle hub without transmission of substantial torque from the needle guard to the needle hub when a torque is applied to the needle guard in a second direction opposite the first direction.
In a further preferred embodiment according to the present invention, there is provided apparatus for releasably securing a needle to a fitting at one end of a syringe comprising a needle hub having a needle projecting from one end thereof and a passage through the needle for transmission of a fluid, the needle hub having a surface for engaging the fitting of the syringe when the hub is secured to the fitting, a needle guard including a sleeve closed at one end and open at its opposite end for receiving the needle and at least a portion of the needle hub within the sleeve, a first pair of cooperable surfaces on the needle hub and the needle guard, respectively, and engageable with one another for enabling a force applied to the needle guard in a first axial direction to be transmitted to the hub for securing the needle hub and the syringe fitting to one another and a second pair of cooperable surfaces on the needle hub and the needle guard, respectively, and engageable with one another for enabling a force applied to the needle guard in a second axial direction opposite the first axial direction to be positively transmitted to the hub for removing the needle hub from the syringe fitting.
Accordingly, it is a primary object of the present invention to provide a novel and improved needle guard and needle assembly for use with a syringe having an adapter removable from the barrel end by rotation of the adapter relative to the barrel wherein torque applied to the needle guard and needle assembly upon application of the needle assembly to and its removal from the syringe will be insufficient to cause the adapter to unseat or unthread from the barrel end.